The present invention relates to a semiconductor device including a memory cell and anti-fuse element, particularly to a semiconductor device including a memory cell and anti-fuse element having a gate capacitor of a metal oxide semiconductor field effect transistor (hereinafter abbreviated as MOSFET) type.
In recent years, electric fuse (e-Fuse) elements which can be remedied even after package sealing of semiconductor elements have attracted attentions as elements which are to replace metal fuse elements broadly used in redundancy circuits having redundancy.
In a gate insulation breakdown type which is one of the electric fuse elements, a system in which high electric field is applied to a gate to break down an oxide insulation film is used, a current flows at a programming time, and any current does not flow at an un-programming time.
Therefore, to achieve a function of a fuse, it is necessary to enlarge a difference between leak currents before/after breaking down a gate insulating film for the programming.
Among the gate insulation breakdown type electric fuses (e-Fuses), a gate insulation breakdown type electric fuse (e-Fuse) having a MOSFET structure which can be formed in the same steps as those for a MOSFET element has a very large merit from a viewpoint of a step cost. However, in recent years, with miniaturization, the gate insulating film has been thinned. Even before the programming, much leak current flows.
Therefore, there is a problem that it is difficult to secure the difference between the leak currents before/after the programming.
As patent documents prior to the present application, there are Japanese Patent Application Laid-Open Nos. 2001-308283 and 2003-86768.
As described above, in the anti-fuse element comprising the conventional MOSFET structure, the gate insulating film to be broken at the programming time has been thinned with the miniaturization in recent years. Therefore, there has been a problem that much leak current flows even before the programming, it is difficult to secure the difference of the leak current before/after the programming, and sufficient stability cannot be secured from viewpoints of programming characteristic and reliability.
In this technical field, there has been a demand for a semiconductor device including a memory cell and anti-fuse element having satisfactory programming properties and high reliability, in which electric resistance properties of the gate insulating film of an anti-fuse portion before programming is strengthened without increasing the steps, and accordingly a current difference before/after the programming is easily secured.